Field device case and field device

ABSTRACT

A field device case is a metal field device case where a lead-in part for drawing a cable including an outer shield is provided on a tubular circumferential wall. The field device case includes: a first inner surface which is formed away from an opening end surface of the field device case in an axial direction orthogonal to the opening end surface; a second inner surface which is formed farther away from the opening end surface than the first inner surface in the axial direction; and a cable fixing member which is fixed to the first inner surface and allows the outer shield of the cable drawn by the lead-in part to be in contact with the second inner surface.

BACKGROUND Field of the Invention

The present invention relates to a field device case and a field device.Priority is claimed on Japanese Patent Application No. 2020-182309,filed on Oct. 30, 2020, the contents of which are incorporated herein byreference.

Description of Related Art

As one item of field devices, a vortex flowmeter disclosed in JapaneseUnexamined Patent Application Publication No. 2002-107192 is known. Thevortex flowmeter includes a vessel having a cylindrical side wall and abulkhead provided in the central part of the side wall. The inside ofthe vessel is divided into a terminal box chamber and an amplifierchamber by the side wall and the bulkhead. The terminal box chamber isprovided with a terminal box part having a signal terminal part and apower source terminal part. The amplifier chamber is provided with anamplifier part that processes an input signal and a power source input.

However, an opening end surface of the aforementioned vessel is coveredby a lid. The vessel and the lid are spigot fitted, and a lead-in portfor drawing a cable into the terminal box chamber is disposed at a deepposition away from the opening end surface so as not to overlap afitting part of the lid. In the related art, as a measure against noisein a cable, a braided shield serving as an outer shield is loosened,shield wires thereof are bundled, and a connection terminal is attachedto the shield wires and is connected to a ground portion of a terminalbox part disposed near an opening end. However, this connection methodhas a problem that terminal processing is complicated, so that many workman-hours are required and mistakes are likely to occur.

SUMMARY

A field device case is a metal field device case where a lead-in partfor drawing a cable including an outer shield is provided on a tubularcircumferential wall. The field device case may include: a first innersurface which is formed away from an opening end surface of the fielddevice case in an axial direction orthogonal to the opening end surface;a second inner surface which is formed farther away from the opening endsurface than the first inner surface in the axial direction; and a cablefixing member which is fixed to the first inner surface and allows theouter shield of the cable drawn by the lead-in part to be in contactwith the second inner surface.

Further features and aspects of the present disclosure will becomeapparent from the following detailed description of exemplaryembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a field device according to anembodiment.

FIG. 2 is a partially cut away perspective view showing a state in whicha lid is removed from a cable connection vessel of a converter accordingto an embodiment.

FIG. 3 is a cross-sectional view of a metal case along a lead-in partaccording to an embodiment.

FIG. 4 is a cross-sectional view of the metal case along a cable fixingmember according to an embodiment.

FIG. 5 is an enlarged view of an area A shown in FIG. 4 .

FIG. 6 is a partially broken perspective view showing a state in which afirst lid is removed from a cable connection vessel of a detectoraccording to an embodiment.

DESCRIPTION OF EMBODIMENTS

The embodiments of the present invention will be now described hereinwith reference to illustrative preferred embodiments. Those skilled inthe art will recognize that many alternative preferred embodiments canbe accomplished using the teaching of the present invention and that thepresent invention is not limited to the preferred embodimentsillustrated herein for explanatory purposes.

An aspect of the present invention is to easily take measures againstnoise in a cable without complicated terminal processing in a fielddevice case and a field device where the cable is drawn from acircumferential wall portion away from an opening end surface.

Hereinafter, a field device case and a field device according to anembodiment of the present invention will be described in detail withreference to the drawings. Hereinafter, an overview of an embodiment ofthe present invention will be described first, and then details of anembodiment of the present invention will be described.

[Overview]

The aforementioned vortex flowmeter disclosed in Japanese UnexaminedPatent Application Publication No. 2002-107192 is a measuring instrumentthat measures a flow speed or a flow rate by measuring the frequency ofthe Karman vortex emitted from a vortex generator placed in a piping. Asa method for detecting the vortex frequency, there is a stress detectionmethod in which a stress detection element is disposed above or insidethe vortex generator to detect an alternating lift acting on the vortexgenerator and the frequency of the Karman vortex is measured. A sensoranalog signal from the stress detection element is transferred from adetector to a converter through a sensor lead wire. The analog signaltransferred to the converter is converted into a digital signal.

The vortex flowmeter disclosed in Japanese Unexamined Patent ApplicationPublication No. 2002-107192 is also referred to as an integral typebecause the detector and the converter are integrally formed with eachother. On the other hand, the vortex flowmeter includes a remote typevortex flowmeter in which the detector and the converter are separatedand connected via a cable. In the remote type vortex flowmeter, in orderto take measures against noise in a cable, both the detector and theconverter need to perform the aforementioned complicated terminalprocessing of the cable, so that work man-hours are doubled andparticularly, mistakes are likely to occur.

As a structure for taking measures against noise without performing theterminal processing of the cable, for example, a ground structuredisclosed in Japanese Unexamined Patent Application Publication No.2020-107722 is known. In the ground structure, an outer shield of acable is exposed, and both ends of a clamp portion in contact with theouter shield are screwed to a frame ground. This structure has a problemthat in a field device where a cable is drawn from a deep position awayfrom an opening end surface, screwing work is performed at the deepposition, so workability is not good.

According to an embodiment of the present invention, in a field devicecase and a field device, a cable fixing member is fixed to a first innersurface provided at a shallow position with respect to an opening endsurface, and an outer shield of a cable is pressed against a secondinner surface, which is provided at a position deeper than the firstinner surface, by the cable fixing member to take the ground. With this,it is possible to easily take measures against noise in the cablebecause work can be simply performed at the shallow position withrespect to the opening end surface without complicated terminalprocessing of the cable.

Embodiment

FIG. 1 is a perspective view showing a field device 1 according to anembodiment.

The field device 1 shown in FIG. 1 is a remote type vortex flowmeter andincludes a detector 2, a converter 3, and a cable 4. The cable 4connects between the detector 2 and the converter 3. The detector 2shown in FIG. 1 includes a piping detection portion 10 and a cableconnection vessel 20.

In the following description, an XYZ orthogonal coordinate system may beset and positional relationships between respective members may bedescribed with reference to the XYZ orthogonal coordinate system. It isassumed that an X-axis direction is a direction in which a fluid flowsin the piping detection portion 10. It is assumed that a Z-axisdirection is a direction orthogonal to the X-axis direction and is adirection in which the cable connection vessel 20 is connected to thepiping detection portion 10. It is assumed that a Y-axis direction is adirection orthogonal to the X-axis direction and the Z-axis direction.

The piping detection portion 10 includes a cylindrical piping portion 11extending in the X-axis direction. The piping portion 11 is provided atboth ends thereof with flanges 12 that can be connected to an externalpiping (not shown). Each of the flanges 12 has a plurality of connectionholes 12 a formed therein at intervals in a circumferential directionaround the central axis of the piping portion 11. A pedestal part 13 isstands upright on the circumferential surface of the piping portion 11in the Z-axis direction.

A fixing block 15 for fixing a detection portion 14 is screwed to anupper surface of the pedestal part 13 via bolts 15 a. The detectionportion 14 is formed in a rod shape and is inserted in the Z-axisdirection from the upper surface of the pedestal part 13 to the insideof the piping portion 11. The detection portion 14 includes a stressdetection element (not shown) inside a rod.

The detection portion 14 detects alternate lifting forces, which acts ona vortex generator of the detection portion 14 disposed inside thepiping portion 11, by the stress detection element, measures thefrequency of the Karman vortices, and measures the flow speed or theflow rate of a fluid from the frequency. Note that the detection portion14 may include a sensor that detects not only the flow speed or the flowrate, but also various physical parameters such as temperature,humidity, pressure, vibration, acceleration, and rotational speed.

A holder 16 including a pair of legs straddling the fixing block 15 isscrewed to the upper surface of the pedestal part 13 via bolts 16 a. Thecable connection vessel 20 is screwed to an upper end of the holder 16via bolts 16 b. A sensor lead wire extending from the detection portion14 (stress detection element) is inserted into the cable connectionvessel 20 by passing through the holder 16.

The cable connection vessel 20 includes a tubular metal case 21 (fielddevice case) extending in the Y-axis direction, a first lid 22 fitted toone end of the metal case 21 in the Y-axis direction, and a second lid23 fitted to the other end of the metal case 21 in the Y-axis direction.The metal case 21 is provided with a lead-in part 24 for drawing thecable 4 at an intermediate position in the Y-axis direction where thefirst lid 22 and the second lid 23 do not overlap each other.

The converter 3 includes a cable connection vessel 30 and a converterbody 40. The cable connection vessel 30 includes a bottomed tubularmetal case 31 (field device case) extending in the X-axis direction anda lid 32 fitted to an opening end of the metal case 31 in the X-axisdirection. The metal case 31 includes a connection part 33 that can beconnected to the converter body 40. The metal case 31 is provided with alead-in part 34 (see FIG. 2 to be described below) for drawing the cable4, similarly to the lead-in part 24 described above.

The converter body 40 accommodates a signal converter, which converts ananalog signal output from the detection portion 14 (stress detectionelement) into a digital signal, and the like. The converter body 40includes a tubular metal case 41 extending in the Y-axis direction, afirst lid 42 fitted to one end of the metal case 41 in the Y-axisdirection, and a second lid 43 fitted to the other end of the metal case41 in the Y-axis direction.

Note that the metal case 41 is also provided with a lead-in part 44having a configuration similar to that of the lead-in part 24 describedabove, but the lead-in part 44 draws a cable of an external device (notshown). An analog signal output from the detector 2 is transferred tothe converter 3 through the cable 4, is converted into a digital signalinside the converter body 40, and then is transferred from the lead-inpart 44 to the external device, and the like via a cable (not shown).Note that the sensor output may be temporarily converted into a digitalsignal by the detector 2 side and output and the converter 3 side mayperform arithmetic processing thereon.

FIG. 2 is a partially broken perspective view showing a state in whichthe lid 32 is removed from the cable connection vessel 30 of theconverter 3 according to an embodiment.

As shown in FIG. 2 , the cable connection vessel 30 of the converter 3includes the bottomed tubular metal case 31 extending in the X-axisdirection and the lid 32 that covers an opening end surface 61 of themetal case 31. Hereinafter, a direction (X-axis direction) orthogonal tothe opening end surface 61 of the metal case 31 may be referred to as anaxial direction. The axial direction is a direction in which a centralaxis O1 of the metal case 31 extends.

The metal case 31 includes a circumferential wall 31 a and a bottom wall31 b. On the outer circumferential surface of the circumferential wall31 a, a fitting groove 31 a 1 into which the lid 32 is fitted and aflange 31 a 2 facing the fitting portion of the lid 32 in the axialdirection are formed. Note that the lid 32 may be attached to the outercircumferential surface of the circumferential wall 31 a by screws.

The circumferential wall 31 a is provided with the lead-in part 34 fordrawing the cable 4 inside the metal case 31. The lead-in part 34 isprovided to protrude from the circumferential wall 31 a on the bottomwall 31 b side beyond the flange 31 a 2 in substantially the tangentialdirection (Y-axis direction) with respect to an inner circumferentialsurface of the circumferential wall 31 a so as not to interfere with thelid 32 fitted to the circumferential wall 31 a. The lead-in part 34 isformed with a lead-in port 34 a that communicates with the inside of themetal case 31.

The metal case 31 is provided therein with a terminal box part 50connected to the cable 4 drawn by the lead-in part 34 and a cable fixingmember 70 that fixes the cable 4 to the metal case 31. Hereinafter, theinternal structure of the metal case 31 will be described in detail withreference to FIG. 3 to FIG. 5 .

FIG. 3 is a cross-sectional view of the metal case 31 along the lead-inpart 34 according to an embodiment. FIG. 4 is a cross-sectional view ofthe metal case 31 along the cable fixing member 70 according to anembodiment. FIG. 5 is an enlarged view of an area A shown in FIG. 4 .

As shown in FIG. 4 , inside the metal case 31, a terminal boxinstallation surface 62, a first inner surface 63, a second innersurface 64, and a third inner surface 65 are formed in a stepwise manneraway from the opening end surface 61 in the axial direction (X-axisdirection). The terminal box installation surface 62, the first innersurface 63, the second inner surface 64, and the third inner surface 65are surfaces that do not overlap each other in the plan view along thecentral axis O1 and face the opening end surface 61 side inside themetal case 31.

The terminal box installation surface 62 is formed closest to theopening end surface 61. As shown in FIG. 3 , the terminal box part 50 isscrewed to the terminal box installation surface 62 via a bolt 51. Asshown in FIG. 4 , a cavity part 31A is formed directly below theterminal box part 50. The cavity part 31A communicates with a connectionpassage 33 a inside the connection part 33. The terminal box part 50 isconnected to the converter body 40 side via a cable (not shown) passingthrough the cavity part 31A and the connection passage 33 a.

The first inner surface 63 is provided farther away from the opening endsurface 61 than the terminal box installation surface 62. The cablefixing member 70 is screwed to the first inner surface 63 via a bolt 80.

The second inner surface 64 is provided farther away from the openingend surface 61 than the first inner surface 63. The cable 4 drawn by thelead-in part 34 is pressed against the second inner surface 64 by thecable fixing member 70.

The third inner surface 65 is provided farther away from the opening endsurface 61 than the second inner surface 64. As shown in FIG. 3 , themetal case 31 is provided with a pedestal part 64A that protrudes fromthe third inner surface 65 toward the opening end surface 61 and isprovided with the second inner surface 64 described above. The secondinner surface 64 is disposed at substantially the same position as thelead-in port 34 a of the lead-in part 34 in the X-axis direction. Notethat as shown in FIG. 2 , the first inner surface 63 described above isalso formed at a distal end of the pedestal part 64A.

As shown in FIG. 5 , the cable 4 includes a plurality of internal cables4 a, a central tensile strength body 4 b disposed at the center of theplurality of internal cables 4 a, an outer shield 4 c that surrounds theouter side of the plurality of internal cables 4 a, and a sheath 4 dthat covers the outer side of the outer shield 4 c. As shown in FIG. 3 ,in the cable 4 placed on the second inner surface 64, the sheath 4 dcorresponding to a front portion of the cable 4 is removed to expose theouter shield 4 c.

Furthermore, in the cable 4, the outer shield 4 c ahead of the secondinner surface 64 is removed, and the plurality of internal cables 4 aare separated and connected to the terminal box part 50. The baseportions of the plurality of internal cables 4 a are bundled by a bandcap 4 e. The outer shield 4 c is, for example, a braided shield in whicha metal wire is woven. Note that the outer shield 4 c may be obtained byspirally winding a metal tape or by wrapping a metal sheet like acigarette.

As shown in FIG. 5 , the cable fixing member 70 includes a fixing part71 fixed to the first inner surface 63, a vertical part 72 verticallyprovided from the fixing part 71 toward the second inner surface 64, anda contact part 73 that is bent from the vertical part 72 to come intocontact with the outer shield 4 c. The cable fixing member 70 can beformed, for example, by bending a substantially rectangular metal plateinto a crank shape. Note that the cable fixing member 70 may be a resinmolded component.

The fixing part 71 is fixed to the first inner surface 63 via the bolt80. The metal case 31 is provided with a rotation preventing part 66that prevents the cable fixing member 70 from rotating on the firstinner surface 63. The rotation preventing part 66 has a convex shapethat protrudes from the first inner surface 63 toward the opening endsurface 61 and abuts the side surface of the fixing part 71. Therotation preventing part 66 is provided at a portion corresponding to astepped portion between the terminal box installation surface 62 and thefirst inner surface 63 described above.

The vertical part 72 is bent at a substantially right angle (anglebetween the fixing part 71 and the vertical part 72 is substantially90°) to a side opposite to the opening end surface 61 with respect tothe fixing part 71. The vertical part 72 is not in contact with themetal case 31, but may be in contact with the metal case 31.

The contact part 73 has a first contact portion 73 a that is bent at asubstantially right angle (angle between the vertical part 72 and thecontact part 73 is substantially 90°) to a side away from the sidesurface of the pedestal part 64A with respect to the vertical part 72,and a second contact portion 73 b that is bent at a substantially obtuseangle (angle between the second contact portion 73 b and the firstcontact portion 73 a is substantially 135°) to a side opposite to theopening end surface 61 with respect to the first contact portion 73 a.

As shown in FIG. 5 , the contact part 73 includes at least a secondcontact point P2 and a third contact point P3 that come into contactwith the outer shield 4 c while interposing a center line L therebetweenin the cross-sectional view of the cable 4, the center line L passingthrough a first contact point P1, where the outer shield 4 c and thesecond inner surface 64 come into contact with each other, and a centerpoint O of the cable 4. Specifically, the first contact portion 73 aincludes the second contact point P2. Furthermore, the second contactportion 73 b includes the third contact point P3. That is, the cable 4is fixed at three points.

The second inner surface 64 includes a planar portion 64 a parallel tothe opening end surface 61, and a slope portion 64 b that warps from theplanar portion 64 a toward the opening end surface 61. Note that theslope portion 64 b may be either an inclined surface or a curvedsurface. The slope portion 64 b includes the first contact point P1.When the planar portion 64 a has the first contact point P1, the cable 4having a circular shape can escape to either the left or right by thepressing of the cable fixing member 70. On the other hand, if the slopeportion 64 b includes the first contact point P1, the escape directionof the cable 4 is limited to one direction, so that the cable 4 can bestably pressed. Note that when one of the contact part 73 and the secondinner surface 64 is formed on a concave curved surface and the other oneis a plane, the left and right escape of the cable 4 can be restrainedeven in the case of two-point contact.

In the field device 1 configured as above, as shown in FIG. 2 , thecable fixing member 70 is fixed to the first inner surface 63 providedat a shallow position with respect to the opening end surface 61 of themetal case 31, the outer shield 4 c of the cable 4 is pressed againstthe second inner surface 64, which is provided at a position deeper thanthe first inner surface 63, by the cable fixing member 70 to take theground. With this, it is possible to easily take measures against noisein the cable 4 because the cable fixing member 70 can be attached at theshallow position with respect to the opening end surface 61 withoutcomplicated terminal processing of the cable 4.

As described above, the present embodiment described above adopts aconfiguration in which in the metal case 31 of the field device 1, wherethe lead-in part 34 for drawing the cable 4 including the outer shield 4c is provided on the tubular circumferential wall 31 a, the first innersurface 63, which is provided away from the opening end surface 61 ofthe metal case 31 in the axial direction orthogonal to the opening endsurface 61, and the second inner surface 64, which is provided fartheraway from the opening end surface 61 than the first inner surface 63 inthe axial direction, are formed, and the metal case 31 includes thecable fixing member 70 that is fixed to the first inner surface 63 andallows the outer shield 4 c of the cable 4 drawn by the lead-in part 34to be in contact with the second inner surface 64. Consequently, in thefield device 1 where the cable 4 is drawn from the portion of thecircumferential wall 31 a away from the opening end surface 61, it ispossible to easily take measures against noise in the cable 4 withoutcomplicated terminal processing.

Furthermore, in the present embodiment, as shown in FIG. 5 , the metalcase 31 is provided with the rotation preventing part 66 that preventsthe cable fixing member 70 from rotating on the first inner surface 63.According to such a configuration, the rotation of the cable fixingmember 70 around the bolt 80 can be restrained. Therefore, the cablefixing member 70 can stably press the cable 4.

Furthermore, in the present embodiment, the rotation preventing part 66has a convex shape that protrudes from the first inner surface 63 towardthe opening end surface 61 and abuts the side surface of the cablefixing member 70. According to such a configuration, the side surface ofthe cable fixing member 70 abuts the convex shape of the rotationpreventing part 66, so that the rotation of the cable fixing member 70can be restrained by a simple structure.

Furthermore, in the present embodiment, the cable fixing member 70includes at least the second contact point P2 and the third contactpoint P3 that conic into contact with the outer shield 4 c whileinterposing the center line L therebetween in the cross-sectional viewof the cable 4, the center line L passing through the first contactpoint P1, where the outer shield 4 c and the second inner surface 64come into contact with each other, and the center point O of the cable4. According to such a configuration, the cable 4 can be stably fixed atthree points. Note that if the cable 4 can be fixed at least threepoints, the cable 4 may be fixed at four points or more.

Furthermore, in the present embodiment, as shown in FIG. 3 , the metalcase 31 is provided with the third inner surface 65, which is providedfarther away from the opening end surface 61 than the second innersurface 64, and the pedestal part 64A, which protrudes from the thirdinner surface 65 toward the opening end surface 61 and is provided withthe second inner surface 64, in the axial direction. According to such aconfiguration, the pedestal part 64A is erected from the third innersurface 65 and the second inner surface 64 is formed to havesubstantially the same depth as the lead-in port 34 a of the cable 4, sothat the outer shield 4 c of the cable 4 can be pressed against thesecond inner surface 64 to take the ground without applying forciblebending and the like to the cable 4.

Note that as shown in FIG. 6 , the metal case 21 of the cable connectionvessel 20 of the detector 2 also has a structure substantially similarto that of the metal case 31 described above.

FIG. 6 is a partially broken perspective view showing a state in whichthe first lid 22 is removed from the cable connection vessel 20 of thedetector 2 according to an embodiment.

As shown in FIG. 6 , the cable connection vessel 20 of the detector 2includes the tubular metal case 21 extending in the Y-axis direction.The metal case 21 is formed on the outer circumferential wall 21 athereof with a fitting groove 21 a 1 into which the first lid 22 isfitted and a flange 21 a 2 facing the fitting portion of the first lid22 in the Y-axis direction.

Hereinafter, a direction (Y-axis direction) orthogonal to an opening endsurface 91 of the metal case 21 may be referred to as an axialdirection. The axial direction is a direction in which a central axis O2of the metal case 21 extends. Inside the metal case 21, a first innersurface 92 and a second inner surface 93 are formed away from theopening end surface 91 in the axial direction (Y-axis direction). Thefirst inner surface 92 and the second inner surface 93 are surfaces thatdo not overlap each other in the plan view along the central axis O2 andface the opening end surface 91 side inside the metal case 21.

A terminal box part 50A and a terminal box part 50B are installed on thefirst inner surface 92, and the fixing part 71 of the cable fixingmember 70 is screwed via the bolt 80. The second inner surface 93 isprovided farther away from the opening end surface 91 than the firstinner surface 92. The second inner surface 93 is an inner wall surfaceof a lead-in port 24 a that draws the cable 4 inside the metal case 21.Note that the terminal box part 50A and the terminal box part 50B may befixed to a surface closer to the opening end surface 91 than the cablefixing member 70 and may include the rotation preventing part 66described above. Furthermore, the terminal box part 50A and the terminalbox part SOB themselves may prevent the cable fixing member 70 fromrotating.

Even in such a configuration, the cable fixing member 70 may be fixed tothe first inner surface 92 provided at a shallow position with respectto the opening end surface 91 of the metal case 21, and the outer shield4 c of the cable 4 may be pressed against the second inner surface 93,which is provided at a position deeper than the first inner surface 92,by the cable fixing member 70 to take the ground. With this, it ispossible to easily take measures against noise in the cable 4 becausethe cable fixing member 70 can be attached at the shallow position withrespect to the opening end surface 91 without complicated terminalprocessing of the cable 4.

Although the preferred embodiment of the present invention has beendescribed with reference to the drawings, the present invention is notlimited to the above embodiment. The all shapes and combinations ofrespective constituent members shown in the embodiment described aboveare examples, and can be variously changed on the basis of designrequirements and the like without departing from the gist of the presentinvention.

For example, the above embodiment has described the configuration inwhich the detector 2 that outputs a detection result and the converter 3connected to the detector 2 via the cable 4 are provided, and both thedetector 2 and the converter 3 include metal field device cases (metalcases 21 and 31) including the aforementioned cable fixing member 70,respectively. However, any one of the detector 2 and the converter 3 maybe configured to include the metal field device case including theaforementioned cable fixing member 70.

For example, in the above embodiment, the cable 4 is circular in thecross-sectional view, but may be a quadrangle, other polygons, anellipse, or other variants.

(Supplementary Note)

(1) A field device case according to an aspect of the invention is ametal field device case where a lead-in part for drawing a cableincluding an outer shield is provided on a tubular circumferential wall,and the field device case may include: a first inner surface which isformed away from an opening end surface of the field device case in anaxial direction orthogonal to the opening end surface; a second innersurface which is formed farther away from the opening end surface thanthe first inner surface in the axial direction; and a cable fixingmember which is fixed to the first inner surface and allows the outershield of the cable drawn by the lead-in part to be in contact with thesecond inner surface.

(2) In the field device case disclosed in the above (1), a rotationpreventing part may be formed to prevent the cable fixing member fromrotating on the first inner surface.

(3) In the field device case disclosed in the above (2), the rotationpreventing part may have a convex shape that protrudes from the firstinner surface toward the opening end surface and abuts a side surface ofthe cable fixing member.

(4) In the field device case disclosed in any one of the above (1) to(3), the cable fixing member may include at least a second contact pointand a third contact point that come into contact with the outer shieldwhile a center line is interposed between the second contact point andthe third contact point in the cross-sectional view of the cable, thecenter line passing through a first contact point, where the outershield and the second inner surface come into contact with each other,and a center point of the cable.

(5) The field device case disclosed in the above (4) may furtherinclude: a third inner surface which is formed farther away from theopening end surface than the second inner surface in the axialdirection; and a pedestal part which protrudes from the third innersurface toward the opening end surface and is provided with the secondinner surface.

(6) The field device case disclosed in the above (5) may furtherinclude: a metal case which is bottomed tubular and extending in theaxial direction; and a lid which is fitted to the metal case.

(7) In the field device case disclosed in the above (6), the metal casemay include a circumferential wall and a bottom wall, and a fittinggroove into which the lid is fitted and a flange facing a fittingportion of the lid in the axial direction may be formed on an outercircumferential surface of the circumferential wall.

(8) In the field device case disclosed in the above (7), thecircumferential wall may be provided with the lead-in part, and thelead-in part may be provided to protrude from the circumferential wallon a side of the bottom wall beyond the flange in a tangential directionwith respect to an inner circumferential surface of the circumferentialwall so as not to interfere with the lid fitted to the circumferentialwall.

(9) The field device case disclosed in the above (6) may furtherinclude: a terminal box part which is provided in the metal case and isconnected to the cable drawn by the lead-in part.

(10) The field device case disclosed in the above (9) may furtherinclude: a terminal box installation surface on which the terminal boxpart is installed, and the terminal box installation surface, the firstinner surface, the second inner surface, and the third inner surface maybe surfaces that do not overlap each other in a plan view along acentral axis of the metal case and face the opening end surface insidethe metal case.

(11) In the field device case disclosed in the above (5), the firstinner surface may be formed at a distal end of the pedestal part, andthe second inner surface may be disposed at a same position as a lead-inport of the lead-in part in the axial direction.

(12) In the field device case disclosed in the above (5), the cablefixing member may include: a fixing part which is fixed to the firstinner surface; a vertical part which is vertically provided from thefixing part toward the second inner surface; and a contact part which isbent from the vertical part to come into contact with the outer shield.

(13) In the field device case disclosed in the above (12), the fixingpart may be fixed to the first inner surface via a bolt.

(14) In the field device case disclosed in the above (12), the verticalpart may be bent at a right angle to a side opposite to the opening endsurface with respect to the fixing part.

(15) In the field device case disclosed in the above (12), the contactpart may include: a first contact portion which is bent at a right angleto a side away from a side surface of the pedestal part with respect tothe vertical part; and a second contact portion which is bent at aobtuse angle to a side opposite to the opening end surface with respectto the first contact portion.

(16) In the field device case disclosed in the above (15), the firstcontact portion may include the second contact point; and the secondcontact portion may include the third contact point.

(17) A field device according to an aspect of the invention may include:a detector configured to output a detection result; and a converterconnected to the detector via a cable, and at least one of the detectoror the converter may include the field device case disclosed in any oneof the above (1) to (16).

(18) In the field device disclosed in the above (17), the detector mayinclude: a piping portion in which fluid flows; and a detection portionconfigured to measure a flow speed or a flow rate of the fluid.

(19) In the field device disclosed in the above (18), the detectionportion may be disposed inside the piping portion, and a stressdetection element that measures the flow speed or the flow rate of thefluid may be provided inside the detection portion.

(20) In the field device disclosed in the above (19), the stressdetection element may detect alternate lifting forces acting on a vortexgenerator of the detection portion, may measure a frequency of Karmanvortices, and may measure the flow speed or the flow rate of the fluidfrom the frequency.

According to an aspect of the present invention, it is possible toeasily take measures against noise in a cable without complicatedterminal processing in a field device case and a field device where thecable is drawn from a circumferential wall portion away from an openingend surface.

As used herein, the following directional terms “front, back, above,downward, right, left, vertical, horizontal, below, transverse, row andcolumn” as well as any other similar directional terms refer to thoseinstructions of a device equipped with the present invention.Accordingly, these terms, as utilized to describe the present inventionshould be interpreted relative to a device equipped with the presentinvention.

The term “configured” is used to describe a component, unit or part of adevice includes hardware and/or software that is constructed and/orprogrammed to carry out the desired function.

Moreover, terms that are expressed as “means-plus function” in theclaims should include any structure that can be utilized to carry outthe function of that part of the present invention.

The term “unit” is used to describe a component, unit or part of ahardware and/or software that is constructed and/or programmed to carryout the desired function. Typical examples of the hardware may include,but are not limited to, a device and a circuit.

While preferred embodiments of the present invention have been describedand illustrated above, it should be understood that these are examplesof the present invention and are not to be considered as limiting.Additions, omissions, substitutions, and other modifications can be madewithout departing from the scope of the present invention. Accordingly,the present invention is not to be considered as being limited by theforegoing description, and is only limited by the scope of the claims.

What is claimed is:
 1. A field device case that is a metal field devicecase where a lead-in part for drawing a cable including an outer shieldis provided on a tubular circumferential wall, the field device casecomprising: a first inner surface which is formed away from an openingend surface of the field device case in an axial direction orthogonal tothe opening end surface; a second inner surface which is formed fartheraway from the opening end surface than the first inner surface in theaxial direction; and a cable fixing member which is fixed to the firstinner surface and allows the outer shield of the cable drawn by thelead-in part to be in contact with the second inner surface, wherein thecable fixing member comprises at least a second contact point and athird contact point that come into contact with the outer shield while acenter line is interposed between the second contact point and the thirdcontact point in the cross-sectional view of the cable, the center linepassing through a first contact point, where the outer shield and thesecond inner surface come into contact with each other, and a centerpoint of the cable.
 2. The field device case according to claim 1,wherein a rotation preventing part is formed to prevent the cable fixingmember from rotating on the first inner surface.
 3. The field devicecase according to claim 2, wherein the rotation preventing part has aconvex shape that protrudes from the first inner surface toward theopening end surface and abuts a side surface of the cable fixing member.4. The field device case according to claim 1, further comprising: athird inner surface which is formed farther away from the opening endsurface than the second inner surface in the axial direction; and apedestal part which protrudes from the third inner surface toward theopening end surface and is provided with the second inner surface. 5.The field device case according to claim 4, further comprising: a metalcase which is bottomed tubular and extending in the axial direction; anda lid which is fitted to the metal case.
 6. The field device caseaccording to claim 5, wherein the metal case comprises a circumferentialwall and a bottom wall, and wherein a fitting groove into which the lidis fitted and a flange facing a fitting portion of the lid in the axialdirection are formed on an outer circumferential surface of thecircumferential wall.
 7. The field device case according to claim 6,wherein the circumferential wall is provided with the lead-in part, andwherein the lead-in part is provided to protrude from thecircumferential wall on a side of the bottom wall beyond the flange in atangential direction with respect to an inner circumferential surface ofthe circumferential wall so as not to interfere with the lid fitted tothe circumferential wall.
 8. The field device case according to claim 5,further comprising: a terminal box part which is provided in the metalcase and is connected to the cable drawn by the lead-in part.
 9. Thefield device case according to claim 8, further comprising: a terminalbox installation surface on which the terminal box part is installed,wherein the terminal box installation surface, the first inner surface,the second inner surface, and the third inner surface are surfaces thatdo not overlap each other in a plan view along a central axis of themetal case and face the opening end surface inside the metal case. 10.The field device case according to claim 4, wherein the first innersurface is formed at a distal end of the pedestal part, and wherein thesecond inner surface is disposed at a same position as a lead-in port ofthe lead-in part in the axial direction.
 11. The field device caseaccording to claim 4, wherein the cable fixing member comprises: afixing part which is fixed to the first inner surface; a vertical partwhich is vertically provided from the fixing part toward the secondinner surface; and a contact part which is bent from the vertical partto come into contact with the outer shield.
 12. The field device caseaccording to claim 11, wherein the fixing part is fixed to the firstinner surface via a bolt.
 13. The field device case according to claim11, wherein the vertical part is bent at a right angle to a sideopposite to the opening end surface with respect to the fixing part. 14.The field device case according to claim 11, wherein the contact partcomprises: a first contact portion which is bent at a right angle to aside away from a side surface of the pedestal part with respect to thevertical part; and a second contact portion which is bent at a obtuseangle to a side opposite to the opening end surface with respect to thefirst contact portion.
 15. The field device case according to claim 14,wherein the first contact portion comprises the second contact point;and wherein the second contact portion comprises the third contactpoint.
 16. A field device comprising: a detector configured to output adetection result; and a converter connected to the detector via a cable,wherein at least one of the detector or the converter comprises thefield device case according to claim
 1. 17. The field device accordingto claim 16, wherein the detector comprises: a piping portion in whichfluid flows; and a detection portion configured to measure a flow speedor a flow rate of the fluid.
 18. The field device according to claim 17,wherein the detection portion is disposed inside the piping portion, andwherein a stress detection element that measures the flow speed or theflow rate of the fluid is provided inside the detection portion.
 19. Thefield device according to claim 18, wherein the stress detection elementdetects alternate lifting forces acting on a vortex generator of thedetection portion, measures a frequency of Karman vortices, and measuresthe flow speed or the flow rate of the fluid from the frequency.